The present invention relates to a novel process for preparing polymers comprising pendant ketone functional moieties. More particularly the present invention relates to a novel process for preparing such polymers without handling monomers which are highly reactive. The resulting polymers are useful as photodegradable thermoplastics and in blends in which the resulting blend is also photodegradable.
Addition polymers of vinyl monomers particularly vinyl aromatic monomers and vinyl ketone polymers are previously known in the art. In particular such copolymers are disclosed in U.S. Pat. Nos. 1,937,063 and 3,753,952. Further blends of such polymers and other polymers are disclosed in U.S. Pat. No. 3,860,538. Current methods for the preparation of vinyl ketone containing polymers such as are disclosed in the foregoing U.S. patents involve the polymerization of the respective monomers. Disadvantageously vinyl ketone monomers are highly reactive and difficult to stabilize for storage. Special polymerization inhibitor systems have been developed so that these monomers can be stored or shipped safely. Such polymerization inhibitor systems, however, result in increased cost and complexity in the polymerization process. Moreover the vinyl ketone monomers are also highly toxic and can be utilized only under conditions which would insure that no environmental exposure of the monomer occur.
In addition because of the rapid rate at which vinyl ketone monomers polymerize, copolymers having good uniformity of ketone content and physical properties are difficult to prepare, even when employing continuous polymerization techniques. The vinyl ketone monomer is very quickly consumed in the polymerization, so that during the latter stages of the polymerization, polymer containing reduced ketone functionality is prepared. Blending techniques may be employed to achieve a homogeneous mixture of product properties, however, this adds additional cost to the process and is believed to result in less efficient utilization of ketone components with regard to the ultimate objective of polymer photodegradability.
In order to provide improved techniques for the preparation of polymers containing pendant ketone functionality, it is desirable to provide an improved process which avoids difficulties occurring in prior art processes.
It is also desirable to provide a process which will prepare ketone containing polymers having greater uniformity.